00:02
Hello, in this question, we have a group of compounds that we need to name.
00:08
And as we look over the list, we see that each one is composed of a metal and a non -metal.
00:13
So that means all of these are ionic compounds, because ionic compounds are composed of a metal plus a non -metal.
00:24
And they are formed when the metal loses one or more electrons to become an ion, and the non -metal gains one or more electrons to become an ion.
00:34
The metal becomes a positive ion, the non -metal becomes a negative ion.
00:39
And electrons can't just float around lost in space.
00:43
However many electrons, the metal gives up, has to be the number of electrons.
00:48
The non -metal accepts.
00:50
So what that means is when we're writing the formula, the positive, the total, positive and negative charges must add to zero.
01:10
So when we add them together, they must equal zero.
01:12
So with that in mind, let's go ahead and get started, naming, or writing the formulas for these.
01:18
So letter a, we have sodium fluoride.
01:21
First thing is to write the symbols.
01:23
Sodium is n -a.
01:25
Fluoride is f.
01:26
Then we need to look at the charges.
01:28
Sodium is in the first column of the periodic table.
01:30
All of the metals in the first column lose one electron to form ions with a one -plus charge.
01:36
Fluorine is a halogen.
01:38
All of the halogens gain one electron to form an ion with a negative.
01:42
1 charge.
01:44
Therefore, positive 1 and negative 1 add to 0, and this formula is complete.
01:50
All right, so the correct formula for sodium fluoride is just naf.
01:57
Let's look at letter b.
01:59
In letter b, we are putting calcium together with the oxide ion.
02:04
Calcium's in group 2 of the periodic table.
02:07
So when it forms ions, they have a 2 positive charge.
02:11
Oxygen's in group 6.
02:12
It would like to get to eight electrons, so it has six of its own and needs to gain two.
02:19
So we have positive two and negative two.
02:22
Those add up to zero, so we don't need any subscripts.
02:25
And the formula is simply c -a -o.
02:31
All right, it seems simple so far, but i have a feeling we are going to get to some where we're going to have to add some subscripts.
02:37
Let's look at letter c.
02:38
Letter c, potassium sulfide.
02:41
Potassium is k.
02:43
It's in the first column of the periodic tux.
02:45
So it has a one positive charge.
02:48
Sulfur is right underneath oxygen in group 6, so it forms a negative ion with a two negative charge.
02:57
So in order for these charges to add to zero, we only have one positive right now and two negative.
03:04
So that means we need to add a subscript of two on the potassium...